/*
    * Copyright (C) 2009 The Guava Authors
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.google.common.collect;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.base.MoreObjects;
  
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  
  import javax.annotation.Nullable;
  
  /**
   * An immutable {@link SetMultimap} with reliable user-specified key and value
   * iteration order. Does not permit null keys or values.
   *
   * <p>Unlike {@link Multimaps#unmodifiableSetMultimap(SetMultimap)}, which is
   * a <i>view</i> of a separate multimap which can still change, an instance of
   * {@code ImmutableSetMultimap} contains its own data and will <i>never</i>
   * change. {@code ImmutableSetMultimap} is convenient for
   * {@code public static final} multimaps ("constant multimaps") and also lets
   * you easily make a "defensive copy" of a multimap provided to your class by
   * a caller.
   *
   * <p><b>Note:</b> Although this class is not final, it cannot be subclassed as
   * it has no public or protected constructors. Thus, instances of this class
   * are guaranteed to be immutable.
   *
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
   * immutable collections</a>.
   *
   * @author Mike Ward
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible(serializable = true, emulated = true)
  public class ImmutableSetMultimap<K, V>
      extends ImmutableMultimap<K, V>
      implements SetMultimap<K, V> {
  
    /** Returns the empty multimap. */
    // Casting is safe because the multimap will never hold any elements.
    @SuppressWarnings("unchecked")
    public static <K, V> ImmutableSetMultimap<K, V> of() {
      return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
    }
  
    /**
     * Returns an immutable multimap containing a single entry.
     */
    public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
      ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
      builder.put(k1, v1);
      return builder.build();
    }
  
    /**
     * Returns an immutable multimap containing the given entries, in order.
     * Repeated occurrences of an entry (according to {@link Object#equals}) after
     * the first are ignored.
     */
    public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) {
      ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
      builder.put(k1, v1);
      builder.put(k2, v2);
      return builder.build();
    }
  
    /**
     * Returns an immutable multimap containing the given entries, in order.
     * Repeated occurrences of an entry (according to {@link Object#equals}) after
     * the first are ignored.
     */
    public static <K, V> ImmutableSetMultimap<K, V> of(
        K k1, V v1, K k2, V v2, K k3, V v3) {
      ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
      builder.put(k1, v1);
     builder.put(k2, v2);
     builder.put(k3, v3);
     return builder.build();
   }
 
   /**
    * Returns an immutable multimap containing the given entries, in order.
    * Repeated occurrences of an entry (according to {@link Object#equals}) after
    * the first are ignored.
    */
   public static <K, V> ImmutableSetMultimap<K, V> of(
       K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
     ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
     builder.put(k1, v1);
     builder.put(k2, v2);
     builder.put(k3, v3);
     builder.put(k4, v4);
     return builder.build();
   }
 
   /**
    * Returns an immutable multimap containing the given entries, in order.
    * Repeated occurrences of an entry (according to {@link Object#equals}) after
    * the first are ignored.
    */
   public static <K, V> ImmutableSetMultimap<K, V> of(
       K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
     ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
     builder.put(k1, v1);
     builder.put(k2, v2);
     builder.put(k3, v3);
     builder.put(k4, v4);
     builder.put(k5, v5);
     return builder.build();
   }
 
   // looking for of() with > 5 entries? Use the builder instead.
 
   /**
    * Returns a new {@link Builder}.
    */
   public static <K, V> Builder<K, V> builder() {
     return new Builder<K, V>();
   }
 
   /**
    * Multimap for {@link ImmutableSetMultimap.Builder} that maintains key
    * and value orderings and performs better than {@link LinkedHashMultimap}.
    */
   private static class BuilderMultimap<K, V> extends AbstractMapBasedMultimap<K, V> {
     BuilderMultimap() {
       super(new LinkedHashMap<K, Collection<V>>());
     }
     @Override Collection<V> createCollection() {
       return Sets.newLinkedHashSet();
     }
     private static final long serialVersionUID = 0;
   }
 
   /**
    * A builder for creating immutable {@code SetMultimap} instances, especially
    * {@code public static final} multimaps ("constant multimaps"). Example:
    * <pre>   {@code
    *
    *   static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
    *       new ImmutableSetMultimap.Builder<String, Integer>()
    *           .put("one", 1)
    *           .putAll("several", 1, 2, 3)
    *           .putAll("many", 1, 2, 3, 4, 5)
    *           .build();}</pre>
    *
    * <p>Builder instances can be reused; it is safe to call {@link #build} multiple
    * times to build multiple multimaps in series. Each multimap contains the
    * key-value mappings in the previously created multimaps.
    *
    * @since 2.0 (imported from Google Collections Library)
    */
   public static final class Builder<K, V>
       extends ImmutableMultimap.Builder<K, V> {
     /**
      * Creates a new builder. The returned builder is equivalent to the builder
      * generated by {@link ImmutableSetMultimap#builder}.
      */
     public Builder() {
       builderMultimap = new BuilderMultimap<K, V>();
     }
 
     /**
      * Adds a key-value mapping to the built multimap if it is not already
      * present.
      */
     @Override public Builder<K, V> put(K key, V value) {
       builderMultimap.put(checkNotNull(key), checkNotNull(value));
       return this;
     }
 
     /**
      * Adds an entry to the built multimap if it is not already present.
      *
      * @since 11.0
      */
     @Override public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
       builderMultimap.put(
           checkNotNull(entry.getKey()), checkNotNull(entry.getValue()));
       return this;
     }
 
     @Override public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
       Collection<V> collection = builderMultimap.get(checkNotNull(key));
       for (V value : values) {
         collection.add(checkNotNull(value));
       }
       return this;
     }
 
     @Override public Builder<K, V> putAll(K key, V... values) {
       return putAll(key, Arrays.asList(values));
     }
 
     @Override public Builder<K, V> putAll(
         Multimap<? extends K, ? extends V> multimap) {
       for (Entry<? extends K, ? extends Collection<? extends V>> entry
           : multimap.asMap().entrySet()) {
         putAll(entry.getKey(), entry.getValue());
       }
       return this;
     }
 
     /**
      * {@inheritDoc}
      *
      * @since 8.0
      */
     @Override
     public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
       this.keyComparator = checkNotNull(keyComparator);
       return this;
     }
 
     /**
      * Specifies the ordering of the generated multimap's values for each key.
      *
      * <p>If this method is called, the sets returned by the {@code get()}
      * method of the generated multimap and its {@link Multimap#asMap()} view
      * are {@link ImmutableSortedSet} instances. However, serialization does not
      * preserve that property, though it does maintain the key and value
      * ordering.
      *
      * @since 8.0
      */
     // TODO: Make serialization behavior consistent.
     @Override
     public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
       super.orderValuesBy(valueComparator);
       return this;
     }
 
     /**
      * Returns a newly-created immutable set multimap.
      */
     @Override public ImmutableSetMultimap<K, V> build() {
       if (keyComparator != null) {
         Multimap<K, V> sortedCopy = new BuilderMultimap<K, V>();
         List<Map.Entry<K, Collection<V>>> entries = Lists.newArrayList(
             builderMultimap.asMap().entrySet());
         Collections.sort(
             entries,
             Ordering.from(keyComparator).<K>onKeys());
         for (Map.Entry<K, Collection<V>> entry : entries) {
           sortedCopy.putAll(entry.getKey(), entry.getValue());
         }
         builderMultimap = sortedCopy;
       }
       return copyOf(builderMultimap, valueComparator);
     }
   }
 
   /**
    * Returns an immutable set multimap containing the same mappings as
    * {@code multimap}. The generated multimap's key and value orderings
    * correspond to the iteration ordering of the {@code multimap.asMap()} view.
    * Repeated occurrences of an entry in the multimap after the first are
    * ignored.
    *
    * <p>Despite the method name, this method attempts to avoid actually copying
    * the data when it is safe to do so. The exact circumstances under which a
    * copy will or will not be performed are undocumented and subject to change.
    *
    * @throws NullPointerException if any key or value in {@code multimap} is
    *     null
    */
   public static <K, V> ImmutableSetMultimap<K, V> copyOf(
       Multimap<? extends K, ? extends V> multimap) {
     return copyOf(multimap, null);
   }
 
   private static <K, V> ImmutableSetMultimap<K, V> copyOf(
       Multimap<? extends K, ? extends V> multimap,
       Comparator<? super V> valueComparator) {
     checkNotNull(multimap); // eager for GWT
     if (multimap.isEmpty() && valueComparator == null) {
       return of();
     }
 
     if (multimap instanceof ImmutableSetMultimap) {
       @SuppressWarnings("unchecked") // safe since multimap is not writable
       ImmutableSetMultimap<K, V> kvMultimap
           = (ImmutableSetMultimap<K, V>) multimap;
       if (!kvMultimap.isPartialView()) {
         return kvMultimap;
       }
     }
 
     ImmutableMap.Builder<K, ImmutableSet<V>> builder = ImmutableMap.builder();
     int size = 0;
 
     for (Entry<? extends K, ? extends Collection<? extends V>> entry
         : multimap.asMap().entrySet()) {
       K key = entry.getKey();
       Collection<? extends V> values = entry.getValue();
       ImmutableSet<V> set = valueSet(valueComparator, values);
       if (!set.isEmpty()) {
         builder.put(key, set);
         size += set.size();
       }
     }
 
     return new ImmutableSetMultimap<K, V>(
         builder.build(), size, valueComparator);
   }
 
   /**
    * Returned by get() when a missing key is provided. Also holds the
    * comparator, if any, used for values.
    */
   private final transient ImmutableSet<V> emptySet;
 
   ImmutableSetMultimap(ImmutableMap<K, ImmutableSet<V>> map, int size,
       @Nullable Comparator<? super V> valueComparator) {
     super(map, size);
     this.emptySet = emptySet(valueComparator);
   }
 
   // views
 
   /**
    * Returns an immutable set of the values for the given key.  If no mappings
    * in the multimap have the provided key, an empty immutable set is returned.
    * The values are in the same order as the parameters used to build this
    * multimap.
    */
   @Override public ImmutableSet<V> get(@Nullable K key) {
     // This cast is safe as its type is known in constructor.
     ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);
     return MoreObjects.firstNonNull(set, emptySet);
   }
 
   private transient ImmutableSetMultimap<V, K> inverse;
 
   /**
    * {@inheritDoc}
    *
    * <p>Because an inverse of a set multimap cannot contain multiple pairs with
    * the same key and value, this method returns an {@code ImmutableSetMultimap}
    * rather than the {@code ImmutableMultimap} specified in the {@code
    * ImmutableMultimap} class.
    *
    * @since 11.0
    */
   public ImmutableSetMultimap<V, K> inverse() {
     ImmutableSetMultimap<V, K> result = inverse;
     return (result == null) ? (inverse = invert()) : result;
   }
 
   private ImmutableSetMultimap<V, K> invert() {
     Builder<V, K> builder = builder();
     for (Entry<K, V> entry : entries()) {
       builder.put(entry.getValue(), entry.getKey());
     }
     ImmutableSetMultimap<V, K> invertedMultimap = builder.build();
     invertedMultimap.inverse = this;
     return invertedMultimap;
   }
 
   /**
    * Guaranteed to throw an exception and leave the multimap unmodified.
    *
    * @throws UnsupportedOperationException always
    * @deprecated Unsupported operation.
    */
   @Deprecated @Override public ImmutableSet<V> removeAll(Object key) {
     throw new UnsupportedOperationException();
   }
 
   /**
    * Guaranteed to throw an exception and leave the multimap unmodified.
    *
    * @throws UnsupportedOperationException always
    * @deprecated Unsupported operation.
    */
   @Deprecated @Override public ImmutableSet<V> replaceValues(
       K key, Iterable<? extends V> values) {
     throw new UnsupportedOperationException();
   }
 
   private transient ImmutableSet<Entry<K, V>> entries;
 
   /**
    * Returns an immutable collection of all key-value pairs in the multimap.
    * Its iterator traverses the values for the first key, the values for the
    * second key, and so on.
    */
   @Override public ImmutableSet<Entry<K, V>> entries() {
     ImmutableSet<Entry<K, V>> result = entries;
     return (result == null)
         ? (entries = new EntrySet<K, V>(this))
         : result;
   }
   
   private static final class EntrySet<K, V> extends ImmutableSet<Entry<K, V>> {
     private transient final ImmutableSetMultimap<K, V> multimap;
     
     EntrySet(ImmutableSetMultimap<K, V> multimap) {
       this.multimap = multimap;
     }
 
     @Override
     public boolean contains(@Nullable Object object) {
       if (object instanceof Entry) {
         Entry<?, ?> entry = (Entry<?, ?>) object;
         return multimap.containsEntry(entry.getKey(), entry.getValue());
       }
       return false;
     }
 
     @Override
     public int size() {
       return multimap.size();
     }
 
     @Override
     public UnmodifiableIterator<Entry<K, V>> iterator() {
       return multimap.entryIterator();
     }
 
     @Override
     boolean isPartialView() {
       return false;
     }    
   }
 
   private static <V> ImmutableSet<V> valueSet(
       @Nullable Comparator<? super V> valueComparator,
       Collection<? extends V> values) {
     return (valueComparator == null)
         ? ImmutableSet.copyOf(values)
         : ImmutableSortedSet.copyOf(valueComparator, values);
   }
 
   private static <V> ImmutableSet<V> emptySet(
       @Nullable Comparator<? super V> valueComparator) {
     return (valueComparator == null)
         ? ImmutableSet.<V>of()
         : ImmutableSortedSet.<V>emptySet(valueComparator);
   }
 
   @Nullable Comparator<? super V> valueComparator() {
     return emptySet instanceof ImmutableSortedSet
         ? ((ImmutableSortedSet<V>) emptySet).comparator()
         : null;
   }
 }